1. Field of the Invention
The present invention relates to perimeters for measuring the visual field of a human eye, and more particularly, the present invention relates to a computer controlled perimetry system for accurately measuring the dynamic and/or static visual field of a patient easily and quickly and without requiring skill, and for recording and storing the measured data.
2. Description of the Related Art
Hitherto, a so-called Goldmann perimeter has been widely used for many years as a measuring apparatus for measuring the visual field of a patient, since the visual field serves as an indicator of glaucoma or brain cancer. This perimeter is effectively used for diagnosing glaucoma since it can accurately measure the dynamic and quantitative visual field of one or both eyes of a patient and thus serves to diagnose glaucoma or to keep track of the progress of the glaucoma. Also, the perimeter is used as an important diagnostic apparatus in the fields of neurosurgery as well as ophthalmology, since some brain cancers can be detected at early developments of those by the perimeter because brain disorders cause changes in the visual field.
FIGS. 1 and 2 are front and rear views, respectively, of the Goldmann perimeter. As shown in FIGS. 1 and 2, the Goldmann perimeter has a dome 1 having a hemispherical inner surface, a projector 2 which projects a light spot and sweeps it from any one point A to any other point B on the inner surface of the dome 1 toward the center of the dome 1, an arm 3 for moving the projector 2 so as to horizontally trace a semicircle along the surface of a virtual hemisphere opposite to the dome 1, and a pantograph 4 for changing the direction of the arm 3 and the projecting direction of the projector 2.
It is assumed that a patient has his head immobilized on a headrest 5 disposed in the dome 1, closes one of his eyes, and stares at a hole 6 disposed in the center of the inner surface of the dome 1. In this state, as shown in FIG. 2 illustrating the rear side of the perimeter shown in FIG. 1, while checking the direction of the face, i.e., the direction of the line of sight, of the patient with a telescope 7 disposed on the rear side of the hole 6, a laboratory technician grips a gripper 8 disposed at the end of the pantograph 4 and moves it from one point on a recording chart 9, corresponding to the point A, to another point on the recording chart 9, corresponding to the point B. The recording chart 9 has a similar shape to that of the inner surface of the dome 1. Then, in response to the movement of the gripper 8, a light spot projected from the projector 2 gradually moves from the point A to the point B on the inner surface of the dome 1 with the aid of the pantograph 4, as shown in FIG. 1.
Upon observing the light spot, the patient notifies the laboratory technician by pushing a buzzer 24 in his hand that he has observed the light spot. The laboratory technician records the point B visually identified by the patient on the recording chart 9 with a recording kit provided on the rear side of the gripper 8. By repeating the foregoing projection and sweeping of the light spot along 16 radial lines shown in FIG. 2, the visual field 22 of the patient is recorded on the recording chart 9, as shown in FIG. 2. Such a measurement for obtaining the visual field can be performed for one or both eyes. Since the operation of such a perimeter is well known to those skilled in the art, further description thereof is omitted.
In addition to the above described components, as shown in FIGS. 1 and 2, the perimeter has a chin-rest plate 15 disposed in the headrest 5 for the patient to put his chin thereon, a belt 16 disposed on the headrest 5 for immobilizing the head of the patient, a shaft 17 disposed at the top of the perimeter serving as a rotating axis of the arm 3, a rotating knob 19 disposed at the rear lower part of the perimeter for adjusting the headrest 5, and a light source 20 disposed at the front upper part of the perimeter for illuminating the projector 2.
In order to measure the visual field of a patient with the above described perimeter, a laboratory technician must hold the gripper 8 and accurately move the pantograph 4 and the arm 3 at a fixed projecting rate while checking the posture, i.e., the line of sight, of the patient. Thus, such a perimeter causes a problem in that the number of patients that can be tested per day is limited since the laboratory technician operating the perimeter is required to be highly skilled. Furthermore, the laboratory technician often becomes extremely fatigued. Accordingly, the perimeter is not effectively used for patients even though it has some excellent functions.
Accordingly, it is an object of the present invention to provide a computer controlled perimetry system, which can be easily and accurately operated even by an unskilled laboratory technician or a doctor, for measuring the visual field of a patient, and also with which a large number of patients can be effectively tested.
The present invention is made to achieve the above-mentioned object. That is, a perimetry system according to the present invention comprises a dome having a hemispherical inner surface; a projector projecting a light spot onto the inner surface of the dome; an arm for horizontally moving the projector so as to trace a semicircle along the surface of a virtual hemisphere opposite to the dome; a first motor for driving the arm; a second motor for changing the projecting direction of the projector; a liquid crystal display for displaying the light spot projected onto the inner surface of the dome; a monitor display for observing a patient; and a computer storing a program for controlling the rotation of the first and second motors. Thus, the light spot projected by the projector can be swept to any point on the inner surface of the dome.
In the perimetry system according to the present invention, the computer for controlling the rotation of the first and second motors may store an additional program by which the arm and the projector move in concert so as to sweep the light spot from one point to another point on the inner surface of the dome, corresponding to the movement of an operator""s finger which touches the liquid crystal display.
Furthermore, the perimetry system according to the present invention may further comprise a first controller for controlling the illuminance of the light spot projected onto the inner surface of the dome.
Moreover, the perimetry system according to the present invention may further comprise a second controller for controlling the size of the light spot projected onto the inner surface of the dome.
As described above, the perimetry system according to the present invention can be easily operated even by an unskilled laboratory technician or a doctor, for accurately measuring dynamic and static visual fields of a patient. In addition, a large number of patients can be effectively examined.